Backset adjusting device of cylindrical door lock

Abstract

A backset adjusting device of a cylindrical door lock. This device free adjusts the backset of the door lock between the 60 mm backset and the 70 mm backset and lets the door lock be commonly used in the conventional doors regardless of the door types. A latch bolt extension slide coupled to a latch bolt has an axial guide slot. A retractor slide is coupled to the latch bolt extension slide so as to linearly reciprocate with respect to the extension slide by 10 mm. This retractor slide has an opened axial guide slit at its front section and a side guide projection movably received in the guide slot of the extension slide for guiding the axial reciprocation of the retractor slide with respect to the extension slide. A pair of hooking notches are formed on the rear section of the retractor slide. An outer cylinder is movably fitted over a rear section of an inner cylinder and coupled to the hooking notches of the retractor slide. This outer cylinder axially moves with respect to the inner cylinder while trailing the retractor slide, thus to adjust the backset of a dead bolt of the door lock between 60 mm backset and 70 mm backset.

What is claimed is: 
     
       1. A backset adjusting device of a cylindrical door lock comprising: a latch bolt, said bolt having an enlarged cavity at its rear center;   a latch bolt extension slide received in said cavity of the latch bolt at its front section and coupled to said latch bolt by a fixing pin, said extension slide having an axial guide slot;   a retractor slide received in said cavity of the latch bolt at its front section in parallel with said latch bolt extension slide and movably coupled to said latch bolt extension slide so as to linearly reciprocate with respect to said extension slide by 10 mm, said retractor slide having: an opened axial guide slit, said guide slit being formed on a front section of the retractor slide and receiving said fixing pin therein;   a side guide projection extending from a side surface of a middle section of the retractor slide toward the extension slide, said side guide projection being movably received in said guide slot of the extension slide in order to slide in said guide slot and to guide axial reciprocation of the retractor slide with respect to the extension slide; and   a pair of hooking notches formed on a rear section of the retractor slide;     an inner cylinder axially receiving both said extension slide and said retractor slide such that rear sections of said slides protrude out of a rear end of said inner cylinder; and   an outer cylinder movably fitted over a rear section of said inner cylinder and coupled to said hooking notches of the retractor slide at its rear end, said outer cylinder axially moving with respect to said inner cylinder while trailing said retractor slide, thus to adjust the backset of a dead bolt of said door lock between 60 mm backset and 70 mm backset.   
     
     
       2. The backset adjusting device according to claim 1, wherein said inner cylinder includes: an axial guide hole, said guide hole being formed on a side wall of the inner cylinder; and   an elastic lock piece formed by bending of a plate spring, said lock piece being provided on said side wall at a position backward spaced apart from said guide hole at an angular interval of 45°; and   said outer cylinder includes: a bent insert, said bent insert being formed on a front end of the outer cylinder and downward bent and movably inserted into said guide hole of the inner cylinder; and   a pair of rectangular holes provided on a side wall of said outer cylinder at positions backward spaced apart from said bent insert at an angular interval of 45°, said rectangular holes being axially spaced out at 10 mm interval, one of said rectangular holes elastically receiving said elastic lock piece so as to retain an adjusted backset.     
     
     
       3. The backset adjusting device according to claim 1, further comprising a guard bolt extension slide for both supporting a latch guard bolt and biasing said retractor slide toward said latch bolt extension slide, said guard bolt extension slide being bent at right angle at its front section, thus to form a contact portion for supporting said latch guard bolt.